[Elecraft] K3 and Expert 1K-FA

[Bob Naumann]

" When repairing the THP amps for failed MOSFETs, how do you know with
certainty the ALC line was disconnected by the customer"?

The customers tell us.

73,

Bob W5OV




-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Paul Christensen
Sent: Wednesday, April 21, 2010 10:14 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3 and Expert 1K-FA

> Do people blast the inputs of their SS amps with 200w or 400w? You bet 
> they
> do. They fry the FETs immediately too.

And that can occur whether or not an ALC line is used between the 
transceiver and amp since ALC is a feedback function and the response time 
back to the transceiver, and the response time of the transceiver, is not 
instantaneous.

> We see them on a fairly frequent
> basis and we have gotten adept at swapping out FETs quickly - at 
> significant
> expense to the owner of the amp. In the vast majority of cases, they had 
> ALC
> disconnected and made a mistake when switching antenna outputs from these
> high-power transceivers.

When repairing the THP amps for failed MOSFETs, how do you know with 
certainty the ALC line was disconnected by the customer?  Also, what is the 
typical ALC response time of the THP amplifiers?

I think it would be an interesting exercise to set up multiple transceivers 
across vendors, together with multiple solid-state amps across vendors, and 
measure the total ALC loop time period.

Paul, W9AC

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